1. The Basal Ganglia

2. What are the basal ganglia?
Dorsal Striatum
Caudate nucleus
Putamen
Ventral Striatum
Nucleus Accumbens
Olfactory Tubercle
Globus Pallidus
Internal segment
External segment
Ventral pallidum
Subthalamic nucleus
Substantia nigra
Pars compacta
Pars reticulata
Pedunculopontine nucleus**
Other Terms:
Archistriatum
Paleostriatum
Neostriatum

3. Where are the basal ganglia?

4. Caudate Nucleus
C shaped structure (“tail”)
Lateral wall of lateral ventricle
Head, body and tail

5. Caudate nucleus
Putamen
Nucleus accumbens
Internal capsule
External capsule
Extreme capsule
claustrum
Septum pellucidum
Insular cortex
Corpus callosum

6. Caudate nucleus
Putamen
Globus pallidus external
Globus pallidus internal
Ventral pallidum
Anterior commissure
Substantia innominata
Internal capsule
Lentiform nucleus**

7. Head, body, tail of caudate
anterior and temporal horn of lateral ventricle
Globus pallidus internal and external
Internal capsule, anterior and posterior limbs

8. Caudate nucleus (body and tail)
Putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra
Pars compacta
Pars reticulata

9. Globus pallidus external
Globus pallidus internal
Subthalamic nucleus
Substantia nigra

10. Subthalamic nucleus
Substantia nigra
Ventral tegmental area

11. Rodent Brain

12. Globus pallidus and entopeduncular nucleus vs.
Globus pallidus (external) and Globus pallidus (internal)

13. “Chemical Neuroanatomy” was very important in increasing our understanding of basal ganglia structures
Use of different histochemical and immunocytochemical stains revealed more extensive striatal structures than previously thought
Also caused revised views of basal ganglia structures in non-mammals and pointed to considerable homologies between birds, mammals and reptiles
From Zhou et al., Nature Neuroscience, 4, (2001) 

14. Functions of the basal ganglia
Extrapyramidal motor system
Motor planning, sequencing and learning
Activity of striatal neurons is not sufficiently explained by the stimuli presented or the movements performed, but depends on certain behavioral situations, certain conditions or particularly types of trials
-sensory stimuli but only when the elicit movements
-instruction cues (go-no go)
-memory related cues
-reward (especially ventral striatum)
-self-initiated moves
Basal ganglia distinguished from cerebellum by connections with limbic system

15. Diseases of the Basal Ganglia
Parkinson’s:
Akinesia
Bradykinesia
Resting tremor
Rigidity
Huntington’s disease
Chorea
Psychiatric disturbances
Dementia

16. Cytoarchitecture Main neurotransmitter in basal ganglia is GABA
95% of neurons in neostriatum are medium spiny neurons (rodent)
Contain GABA
Principal neurons: project to globus pallidus and SNpr
Subpopulations are distinguished by peptides, neurotransmitter receptors and connections
Receive bulk of afferent input
Several populations of interneurons
aspiny
ACh, GABA/parvalbumin, GABA/calretinin; GABA/NPY/NADPH/Somatostatin
From Groves, Brain Res. 286: 109, 1983

17. The Neostriatal Mosaic
Neostriatum divided into two compartments: patch (striosome) and matrix
First described by Ann Graybiel in 1978 using AChE stain
Not visible in Nissl stains (“hidden chemoarchitecture”)
Define input/output architecture of neostriatum
From Holt et al., 1997, JCN

18. Connections Afferents (striatum): Efferents (Gpi, VP, SNpr)
Cerebral cortex (entire cortex)
Thalamus (intralaminar and midline nuclei)
Amygdala (basolateral nucleus)
Raphe, substantia nigra pars compacta, VTA
Efferents (Gpi, VP, SNpr)
Ventral tier nuclei of thalamus
Superior colliculus

19. All regions of cerebral cortex project to the basal ganglia, but output of basal ganglia is directed towards the frontal lobe, particularly pre-motor and supplementary motor cortex

20. Basic Circuit of Basal Ganglia
Cerebral Cortex
Neostriatum + +
Gpi/SNpr
Gpe
Subth
VA/VL thalamus

21. Disinhibition
From Chevalier and Deniau, TINS 13:277, 1990

22. Direct vs indirect pathways
Different populations of spiny neurons
Enkephalin vs substance P
D1 vs D2 receptors
From Graybiel, A. Neural Networks, Am J Psychiatry 158:21, January 2001

23. Functional subdivisions
Sensorimotor
Putamen + globus pallidus/SNpr
SNpc
Association
Caudate nucleus + globus pallidus/SNpr
Limbic
Nucleus accumbens + ventral pallidum
VTA
From Parent, TINS 13: 254, 1990

24. Alexander GE, DeLong MR, Strick PL., Annu Rev Neurosci. 1986;9:357-81
Parallel Circuits
Alexander GE, DeLong MR, Strick PL., Annu Rev Neurosci. 1986;9:357-81

25. Neostriatal Mosaic and Input/Output Organization
Most inputs to the neostriatum terminate in a patchy fashion (“matrisomes”)
Input from a given cortical region terminates over an extended anterior-posterior extent
Functionally related cortical areas project to the same patches
Output neurons to a given efferent subregion are also arranged in patches
Neurons in patches project to both Gpi/SNpr and GPe

26. “divergent-reconvergent processing”
Cortex
Neostriatum
Gpi/SNpr
“divergent-reconvergent processing”
From Graybiel et al., The basal ganglia and adaptive motor control, Science, 265: 1826, 1994

27. Direct and Indirect Pathways

28. Facilitation vs inhibition of movement
Albin RL, Young AB, Penney JB. The functional anatomy of basal ganglia disorders.Trends Neurosci Oct;12(10):
Akinetic disorders: overactivity in the indirect pathway
Dopamine increases activity in the direct pathway and decreases activity in the indirect pathway
Loss of dopamine decreases activity in the direct pathway and increase activity in the indirect pathway
Increased activity in the indirect pathway = increased activity in the direct pathway = increased inhibition on thalamus
Hyperkinetic disorder: overactivity in the direct pathway
Projections to the Gpe degenerate early in HD = removal of inhibition = increased activity of indirect pathway
Increased activity of indirect pathway = increased inhibition of subthalamic nucleus = decreased excitatory drive on direct pathway = decreased inhibition on thalamus

29. Summary of Forebrain Systems
Cortical vs subcortical
According to Swanson, the forebrain can be understood in terms of two systems:
Cortex and cortical (basal) nuclei
Cortical: glutamate projection neurons
Striatal: GABA projection neurons
Pallidal: GABA ---> Thalamus --> Cortex